show return the moscow city translated in japanese. in this case there is no translate possible and moscow should be return in english but it is return in russia language.
PlaceFinder returns place names in the desired language if they exist. If they don't exist, the English place names are normally returned. If there are no English place names, place names in the local language for the returned country are returned. There is no way to provide a list of desired languages.
There is a special case for address matches and some city matches where place names in the local language are returned if place names in the desired language do not exist. There is a special case for Russia where a transliterated Latin place name, such as Moskva, is returned if a Cyrillic place name, such as Москва,́ is not available. This should explain why your request returns a mixture of Cyrillic and transliterated Latin place names for your query.
"jp" is not the ISO 639 language code for Japanese; the correct code is "ja". Japanese places names are limited to Japan and a small number of places in other countries.